Time of day does not affect radiologists' visual acuity

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Although a statistically significant difference was detected between the visual acuity of radiologists in the morning compared with other parts of the day, the difference was of such small magnitude that it fell within the expected range of variability, according to a study in the June issue of the American Journal of Roentgenology.

Nabile M. Safdar, MD, and colleagues from the department of diagnostic radiology and nuclear medicine at the University of Maryland School of Medicine in Baltimore said that the purpose of the study was to examine the intermediate-distance visual acuity of a cross section of radiologists and to identify variation in visual acuity during a typical workday.

The researchers collected surveys from 48 radiologists before undergoing visual acuity testing, with corrective lenses if routinely used, at three times of the day.

Safdar and colleagues found that the mean acuity of radiologists across all measurements was 20/15 (logarithm of the minimum angle of resolution [logMAR], -0.109). Visual acuity ranged from 20/30 to 20/10 (logMAR, 0.176 to -0.301). Mean visual acuity in the morning session was approximately 20/16 (logMAR, -0.0856).

They found that this value was statistically significantly lower than the mean visual acuity in both the early afternoon (logMAR, -0.124) and the late afternoon (logMAR, -0.118), both of which were approximately 20/15. This change was within the expected test-retest variability of Snellen acuity measurements.

"It is unlikely that such variation in visual acuity among radiologists influences diagnostic performance," the authors wrote. "Not every radiologist had 20/20 vision, a few needed visual correction, and more than a few had not undergone a thorough eye examination for as many as 15 years before the study."

The authors concluded that future studies must address how and whether shortcomings in visual acuity adversely affect diagnostic accuracy and efficiency, and whether departmental or professional standards should be developed to ensure optimal visual accuracy.